Project Summary This U19 aims to determine how PD-1 blockade affects human immune responses induced by chronic viruses and vaccines. The Clinical Core of the proposed MGH-UPenn PRIG will be central to the scientific efforts of this consortium. A unique and expansive sample repository has been created over the last 18 years and well- characterized for clinical, immune, and genetic data. This repository will be maintained and crucially expanded to include longitudinal samples from individuals undergoing immunotherapies via clinical infrastructures at both MGH and UPenn. This concerted effort will maintain a high throughput of sample availability to catalyze scientific efforts across the consortium, including tracking samples to investigators in Projects 1 and 2 and Cores C and D.